A randomized, double-blind, parallel-group, fixed-dose, clinical trial of quetiapine at 600 versus 1200 mg/d for patients with treatment-resistant schizophrenia or schizoaffective disorder.

Quetiapine is often prescribed at doses higher than those approved by regulatory authorities, with limited evidence from controlled trials. The objective of this study was to assess the safety, tolerability, and efficacy of high-dose quetiapine (1200 mg/d) compared with a standard dose of 600 mg/d among patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, schizophrenia or schizoaffective disorder hospitalized at 2 state-operated psychiatric facilities. In order to be eligible for randomization, subjects were required to prospectively fail to demonstrate an initial therapeutic response during a 4-week run-in phase with quetiapine at 600 mg/d (immediate release and dosed twice a day). Lack of an adequate initial response was defined a 15% or lower decrease in the Positive and Negative Syndrome Scale total score. Patients were then randomized to either continue quetiapine at 600 mg/d for an additional 8 weeks or to receive 1200 mg/d quetiapine instead. No significant differences were observed between the high dose (n = 29) and standard dose (n = 31) groups in change from baseline to endpoint on extrapyramidal symptoms, electrocardiographic changes, or most laboratory measures between groups. There was a significant difference between groups for triglycerides (P = 0.035), and post hoc tests revealed a decrease in triglycerides from baseline (mean [SD], 162.7 [59.3] mg/dL) to endpoint (mean [SD], 134.8 [62.7] mg/dL) for the 600 mg/d group (P = 0.019). The mean change in the Positive and Negative Syndrome Scale total score did not differ between groups. In conclusion, quetiapine at 1200 mg/d, although reasonably tolerated, did not confer any advantages over quetiapine at 600 mg/d among patients who had failed to demonstrate an adequate response to a prospective 4-week trial of 600 mg/d.